Since composite resins have remarkably improved long-term durability and mechanical characteristics and also have characteristics such as fluorine sustained-release and X-ray contrast radiographic properties, composite resins have recently been used for functional and esthetic recovery of tooth substances when deficiency in the tooth substances is caused by the onset of dental caries or when there is a breakage or detachment of a dental crown restoration. Application of these composite resins has expanded to tooth face coating materials, fissure sealants, orthodontic bonding materials, and resin core materials. However, since these composite resins themselves not only have no adhesion, but also have adhesion to ceramics and metals, it is essential to use various bonding materials in combination. It is required for the bonding material to have excellent adhesion to both enamel containing an inorganic component such as hydroxyapatite as a main component and dentin containing an organic component such as collagen as a main component, particularly to the tooth substances. It has recently required for the bonding material to firmly bond to ceramics, metals, resins, composite resins, and glass ionomer cement and to have durability on adhesion.
In a conventional bonding material, after subjecting tooth surfaces to a tooth surface treatment using a strong etching material such as phosphoric acid, the bonding material is applied to bond tooth substances with a composite resin. However, a method for the tooth surface treatment using an acid etching material had a drawback such as complicated operation steps in which the acid applied on the tooth surface must be sufficiently removed by washing with water and the tooth surface dried.
The bonding method using the acid etching material showed sufficient adhesion to enamel as a result of formation of a roughened surface through decalcification of the acid etching material, and macroscopic mechanical fitting based on sufficient penetration and curing of the bonding material. In contrast, since a spongy collagen fiber is exposed to dentin as a result of decalcification of the acid etching material, the bonding material did not sufficiently penetrate into a collagen fiber and it was difficult to obtain sufficient adhesion.
In order to obtain high adhesion to dentin, an acid tooth surface treating material has been proposed which replaces the phosphoric acid etching material. For example, Japanese Unexamined Patent Publication (Kokai) No. 62-33109 discloses a tooth surface treating material containing a sulfonic acid group-containing polymer; Japanese Unexamined Patent Publication (Kokai) No. 62-231652 discloses a tooth surface treating material containing a metal halide; Japanese Unexamined Patent Publication (Kokai) No. 63-279851 discloses a tooth surface treating material containing an amphoteric amino compound; Japanese Unexamined Patent Publication (Kokai) No. 1-279815 discloses a tooth surface treating material containing an organic carboxylic acid and a metal chloride; and Japanese Unexamined Patent Publication (Kokai) No. 5-163111 discloses a tooth surface treating material containing an organic carboxylic acid and an iron phosphate.
However, it was difficult to obtain sufficient adhesion to dentin even when these acid tooth surface treating materials are used.
Japanese Patent No. 2,865,794 specification discloses, as a polymerizable compound having an acid group, an adhesive composition containing (a) a (meth)acrylate ester derivative having a phosphonic acid group, which is represented by the general formula (I):
wherein R1 represents a hydrogen atom or a methyl group, R2 represents an alkylene group having 5 to 10 carbon atoms, and R3 represents an alkylene group having 1 to 6 carbon atoms, (b) at least one kind of a radical polymerizable monomer, and (c) at least one kind of a polymerization initiator. When the phosphonic acid group contained in the (meth)acrylate ester derivative is applied on the dental substance, the phosphonic acid group is chemically bonded with a calcium component of the dental substance and, as a result, the phosphonic acid group can be imparted to the tooth surface. Although adhesion to enamel such as a resin cement can be improved by copolymerizing the polymerizable group with another polymerizable monomer in the resin cement, the resultant copolymer is not bonded to dentin at all.
Since it was presented that a primer is effective for penetration to a collagen fiber exposed by the acid tooth surface treating material applied on the tooth surface [Journal of Dental Research Vol. 63, P1087-1089, 1984: Primer Composition Comprising Glutaraldehyde/2-HEMA/Water], a three-step technique comprising acid treating agent/primer/bonding material has recently been used.
The proposed bonding method involving such a three-step technique includes methods described in Japanese Patent No. 3,399,573 and Japanese Patent No. 2,962,628.
Since 2-HEMA as a water-soluble polymerizable monomer contained in the primer stimulates mucous membranes, a primer composition containing another water-soluble polymerizable monomer to be replaced by 2-HEMA is also disclosed. For example, Japanese Unexamined Patent Publication (Kokai) No. 2004-137211 discloses a primer composition containing polyethylene glycol or polyethylene glycol monomethacrylate, and Japanese Patent No. 2,782,694 discloses a primer composition containing glyceryl mono(meth)acrylate.
However, these bonding techniques include a large number of complicated steps, and although they show high adhesion to enamel, they show insufficient adhesion to dentin.
An adhesive monomer having an acidic group in the molecule has recently been developed and there has been proposed a self-etching primer wherein a complicated operation step capable of simultaneously performing an acid treatment of decalcificating the tooth surface and a treatment of penetrating a primer into a collagen fiber is simplified. In the technique when the primer is used, an acid treatment to the tooth surface is not required and, after completion of a treatment (application/standing) of the tooth surface with the self-etching primer, a bonding material is applied after drying.
By treating the tooth surface, on which cavities are formed, with the self-etching primer, the self-etching primer penetrates into tooth substances (enamel/dentin) while dissolving a smear layer formed as a result of formation of cavities. After drying, the self-etching primer and the bonding material are integrated by applying the bonding material, followed by curing to obtain an adhesive layer.
A lot of proposals were made regarding the composition of these self-etching primers. For example, Japanese Unexamined Patent Publication (Kokai) No. 1-113057 discloses a primer composition comprising water/water-soluble film forming agent/salt of acid; Japanese Patent No. 2,634,276 discloses a primer composition comprising water/polymerizable compound having a hydroxyl group/polymerizable compound having an acid group/curing agent; Japanese Patent No. 3,480,654 and Japanese Patent No. 3,487,389 disclose dental primers comprising water/phosphoric acid group-containing polymerizable monomer/polyhydric carboxylic acid group-containing polymerizable monomer; Japanese Unexamined Patent Publication (Kokai) No. 7-82115 discloses a primer composition comprising vinyl compound having an acidic group/water-soluble vinyl compound having a hydroxyl group/water/aromatic sulfonate-aromatic amine; Japanese Unexamined Patent Publication (Kokai) No. 62-223289 discloses a primer composition comprising 2-HEMA/water containing an organic or inorganic acid; and Japanese Unexamined Patent Publication (Kokai) No. 4-8368 discloses a primer composition comprising water/polymerizable compound having an acid group/polymerizable compound having a hydroxyl group/amino compound having an acid group.
These compositions show a certain degree of adhesion to dentin, but do not show sufficient adhesion to enamel because they exert a poor decalcification action to an inorganic component.
Since the primer composition contains an acidic group-containing polymerizable monomer having poor polymerizability and a water-soluble polymerizable monomer, resulting in insufficient curing after application of the bonding material, and thus a problem such as poor durability on adhesion under a severe intraoral environment has occurred.
Furthermore, since these primer compositions are basically present in an acidic atmosphere where water and an acidic group-containing polymerizable monomer coexist, deterioration and change in quality are caused by hydrolysis of an intramolecular main chain and a functional group in components contained in the primer composition, and thus there were problems such as poor storage stability and material stability. Therefore, it was required to divide into a separate packaging form.
In order to solve these problems, there have been a lot of proposals regarding sufficiently curing an adhesive layer by using a primer and a bonding material in combination to thereby improve dental adhesion. For example, Japanese Unexamined Patent Publication (Kokai) No. 2000-212015 and Japanese Unexamined Patent Publication (Kokai) No. 2000-16911 disclose a dental adhesive system comprising a bonding material containing an acylphosphine oxide compound as a photopolymerization initiator, and a primer composition containing (polymerizable monomer having an acidic group/polymerizable monomer having a hydroxyl group/water); Japanese Unexamined Patent Publication (Kokai) No. 2004-26838 discloses a dental adhesion kit comprising a primer composition containing a phosphoric acid group-containing polymerizable monomer/water, and a bonding material containing a polyhydric carboxylic acid group-containing polymerizable monomer/polymerization initiator; Japanese Patent No. 3,236,030 discloses a novel bonding method using a bonding material comprising a primer solution containing a vinyl monomer having a specific molecular structure having a carboxyl group or an acid anhydride thereof, and an adhesive composition of a vinyl monomer having an acidic group; Japanese Unexamined Patent Publication (Kokai) No. 2000-204010 discloses a dental adhesion kit comprising a primer composition containing a sulfonic acid group-containing polymerizable monomer/water-soluble polymerizable monomer/water, and a bonding material containing an acidic phosphate ester-based polyfunctional polymerizable monomer; Japanese Unexamined Patent Publication (Kokai) No. 9-295313 discloses a dental adhesion kit comprising a primer composition containing sulfonic acid group-containing polymerizable monomer/water-soluble polymerizable monomer/water, and a bonding material containing a polyhydric carboxylic acid group-containing polyfunctional polymerizable monomer; Japanese Unexamined Patent Publication (Kokai) No. 11-180814 discloses a dental substance adhesive set comprising a self-etching primer containing acidic group-containing (meth)acrylate/water-soluble organic solvent/water, and a dental substance adhesive containing (meth)acrylate containing neither an acidic group nor a hydroxyl group/photopolymerization initiator/photopolymerization accelerator/filler; Japanese Unexamined Patent Publication (Kokai) No. 6-24928 discloses an adhesive comprising a primer solution composition containing specific metal compound/acidic group-containing polymerizable monomer/polymerizable monomer, and a curable composition containing trialkylboron or a partial oxide thereof as a polymerization catalyst; and Japanese Patent No. 3,449,755 discloses an adhesive kit comprising a primer composition containing acidic group-containing vinyl polymerizable compound/hydroxyl group-containing water-soluble vinyl compound/water/aromatic amine, and an acrylic adhesive containing acidic group-containing acrylic monomer/acidic group-noncontaining acrylic monomer/polymerization initiator.
All of these proposals enable realization of adhesion to tooth substances (enamel and dentin) by using in combination with a specific bonding material so as to improve curability of a primer composition containing an acidic group-containing polymerizable monomer having poor polymerizability and a water-soluble polymerizable monomer.
However, low curability involved in constituent components of the primer composition cannot be basically improved. Therefore, it is recognized that adhesion to both of enamel and dentin as well as durability on adhesion are insufficient.
Japanese Unexamined Patent Publication (Kokai) No. 10-251115 discloses, as a polymerizable compound having an acid group, a dental primer containing (A) a phosphoric acid group-containing polymerizable monomer having a —C—O—P ester bond, (B) a polyhydric carboxylic acid group-containing polymerizable monomer, and (C) water as main components.
According to this dental primer, a high adhesive strength of 20 MPa or more can be obtained in both dentin and enamel. However, an ester bond in the phosphoric acid group-containing polymerizable monomer used for this primer is likely to be hydrolyzed and is insufficient in storage stability and durability on adhesion.
[Patent Document 1]
Japanese Unexamined Patent Publication (Kokai) No. 62-33109
[Patent Document 2]
Japanese Unexamined Patent Publication (Kokai) No. 62-231652
[Patent Document 3]
Japanese Unexamined Patent Publication (Kokai) No. 63-279851
[Patent Document 4]
Japanese Unexamined Patent Publication (Kokai) No. 1-279815
[Patent Document 5]
Japanese Unexamined Patent Publication (Kokai) No. 5-163111
[Patent Document 6]
Japanese Patent No. 2,865,794 specification
[Patent Document 7]
Japanese Patent No. 3,399,573
[Patent Document 8]
Japanese Patent No. 2,962,628
[Patent Document 9]
Japanese Unexamined Patent Publication (Kokai) No. 2004-137211
[Patent Document 10]
Japanese Patent No. 2,782,694
[Patent Document 11]
Japanese Unexamined Patent Publication (Kokai) No. 1-113057
[Patent Document 12]
Japanese Patent No. 2,634,276
[Patent Document 13]
Japanese Patent No. 3,480,654
[Patent Document 14]
Japanese Patent No. 3,487,389
[Patent Document 15]
Japanese Unexamined Patent Publication (Kokai) No. 7-82115
[Patent Document 16]
Japanese Unexamined Patent Publication (Kokai) No. 62-223289
[Patent Document 17]
Japanese Unexamined Patent Publication (Kokai) No. 4-8368
[Patent Document 18]
Japanese Unexamined Patent Publication (Kokai) No. 2000-212015
[Patent Document 19]
Japanese Unexamined Patent Publication (Kokai) No. 2000-16911
[Patent Document 20]
Japanese Unexamined Patent Publication (Kokai) No. 2004-26838
[Patent Document 21]
Japanese Patent No. 3,236,030
[Patent Document 22]
Japanese Unexamined Patent Publication (Kokai) No. 2000-204010
[Patent Document 23]
Japanese Unexamined Patent Publication (Kokai) No. 9-295913
[Patent Document 24]
Japanese Unexamined Patent Publication (Kokai) No. 11-180814
[Patent Document 25]
Japanese Unexamined Patent Publication (Kokai) No. 6-24928
[Patent Document 26]
Japanese Patent No. 3,449,755
[Patent Document 27]
Japanese Unexamined Patent Publication (Kokai) No. 10-251115
[Non-Patent Document 1]
Journal of Dental Research Vol. 63, P 1087-1089, 1984